1. Technical Field
The present invention relates to a method for controlling direction between a mobile wireless transmission device equipped with a direction control antenna and a fixed wireless transmission device.
2. Description of the Related Art
An omni-directional antenna is generally used as a base station antenna in a mobile communication system to radiate or receive signals equally regardless of direction.
All signals transmitted or received to an antenna are transmitted or received by controlling power according to the distance to a transmission/reception antenna of a base station and interference is caused to transmitted or received desired signals. Thus, an antenna of a base station cannot selectively transmit or receive signals.
Therefore, a cell is divided into several sectors and several antennas are used to reduce such interferences. For example, when a cell is divided into 3 sectors and 3 antennas are used, each antenna is responsible for 120° which is able to reduce the interference by ⅓.
Furthermore, an antenna can be fixed to provide higher gain for the signals transmitted or received from a predetermined angle and provide less gain for the interference signals transmitted or received from different directions in order to reduce the interference. However, this method can be efficient when a receiver/transmitter is fixed.
A smart antenna system is able to selectively transmit or receive signals of a desired direction to minimize interferences and thus significantly reduce interferences between subscribers. That is, an independent beam is provided to each terminal in a cell for receiving and transmitting and beam is provided to a desired terminal so that volume of radiation can be minimized to other direction terminals.
Such a smart antenna system is also able to minimize interfering noises between traffic channels to improve call qualities. The smart antenna system is also able to provide radio wave to a desired direction so that each terminal is allowed for communications in low power.
An optimized beam forming technique is to build an array antenna in a base station to provide independently optimum weight to each subscriber.
Applications of a low power wireless transmission system become diversified and its structure and functions are also simplified. While processing capacities, functions and performances of a conventional mobile communication terminal increase, functions of a communication module such as a wireless transmission device for sensor network, internet of things (IoT) and so on are becoming simplified and low-power consumed.
When a mobile station moves around a fixed station which is able for direction control and communication between these wireless stations (between the mobile station and the fixed station) is made, the fixed station should control the direction according to the movement of the mobile station.
US 2013-0259005 discloses that a fixed station controls direction when a mobile station moves around.
US 2013-0259005 teaches that when RSSI (Received signal strength indicator) values between two terminals are compared, emission zone with higher value is selected.
Even though time required for conversion or on/off of the emission zone is short, when connection between two wireless stations gets disconnected, data exchange to exchange necessary information may not be possible for the time required for reconnection. Thus, a method for reducing reconnection process is demanded.